1. Field of Invention
The present invention relates to a through-the-wall vented forced hot air heater which humidifies and cleans the air without any additional equipment or a water supply and in particular to a counter-current heat and mass transfer device with a ceramic heat and moisture storage and transfer means.
2. Description of the Prior Art
Prior art vented, forced hot air space heaters have a distinct separation of the combustion side from the hot air side. Heat is transferred from the combustion process and the resulting combustion products to the forced air through the walls of a metal containment vessel and its extensions. Thus, the forced hot air temperature is limited to, and generally far below, the service temperature of the metal, which is usually a steel sheet or cast iron. Also these metals offer a limited geometry and surface area for the heat transfer.
In prior art, the exhaust temperature must be sufficiently high to prevent the condensation of the corrosive moisture and to maintain the draft in a flue. Thus a substantial portion, over twenty percent, of the available heat is lost as the sensible and the latent heat of the high temperature exhaust gas. In more recent "energy efficient" heaters, a part of the exhaust heat is recovered by transferring it counter-currently to the incoming combustion air stream.
In prior art industrial processes with high exhaust temperature, a large part of the sensible heat of the exhaust is recovered with a heat recuperator. For space heaters, however, it is neither economical nor practical because of its size and of the pollutants and the relatively low temperature of their exhaust.
Furthermore, in prior art heaters, an accurate control of the combustion process is difficult as the combustion is carried out in a chamber which is surrounded by cooler metal walls, which tend to quench the flame. This causes high levels of harmful CO and other incomplete combustion products, which are discharged via a chimney and pollute the air.
In meeting the requirements of the Clean Air Act Amendment of 1990, a significant improvement of the ambient air quality can be achieved by reducing or preventing the air pollution from the space heaters in winter, especially in the populated northeastern part of this country. An elimination of chimneys from new constructions of homes and factories in the non-attainment areas can prevent the air pollution, improve the ambient air quality and promote more efficient uses of fossil fuels for the space heating. Many advanced emission control technologies, which are developed in auto and other industries during the last two decades, are available for the space heating.
Among the various types of residential heaters, forced hot air heaters are particularly convenient for the humidification of the air, but these require a separate humidifier with its own water supply. Recently, smaller, more thermally efficient through-the-wall vented hot air heaters became popular for renovated apartments. These units eliminate the expensive duct-work and the chimney, allow a separate zone control, and give some savings in the construction and fuel costs. Also with the increasing awareness of indoor air quality, the removal of the indoor air-borne organic contaminants is a necessity, especially for those who are sensitive or allergic to these indoor pollutants. The filters are only marginally effective and the electronic types cost more than the heaters.